For the measurement of a blood pressure, it has been a conventional practice to insert an arm of a measurer into an arm insertion hole formed by a cuff holding a blood flow blocking bag, then to fix the cuff to the arm, and to measure a blood pressure by inflating the blood flow blocking bag to apply a specified pressure (for example, Japanese Unexamined Patent Publication No. H01-254146, Japanese Patent No. 3235602). However, there have been recognized main points to be improved, for example, in order (1) to enable a precise measurement, (2) not to give any feeling of pressure or any feeling of tension of a measurement to a measurer, and (3) to enable an efficient use of a driving energy of a blood pressure monitor. Specifically, there have been the following problems.
An arm to be measured, normally an upper arm is thicker at a shoulder side while being thinner at a wrist side. On the other hand, since a conventional cuff is rectangular, if an attempt is made to fix the cuff to the arm by taking up the cuff by means of a take-up drum, the cuff comes into contact only with the shoulder side of the arm while being not fixed at all at the wrist side. In such a state, no precise blood pressure measurement can be made.
Upon winding the cuff holding the blood flow blocking bag around the arm, an epidermis part of the arm often gets in the cuff. Japanese Patent Publication No. 3233481 proposes a blood pressure monitor in which one end of a cuff holding a blood flow blocking bag is fixed to an arm rest and the other end is coupled to a take-up mechanism to automatically take up the cuff. Japanese Unexamined Utility Model Publication No. H02-37605 proposes a blood pressure monitor of the hand winding type in which a covering member for covering a measurement part at an inserting side of a folded member in order to prevent an epidermis part of an arm from getting in a cuff. However, with the blood pressure monitor having the automatic take-up mechanism, the epidermis part of the arm may be pulled by the cuff being taken up and may get in between lateral portions of the arm rest and the cuff when the cuff is taken up by the automatic take-up mechanism. The blood pressure monitor of the hand winding type has a problem of being inconvenient and taking much labor because the cuff is hand-wound.
On the other hand, in the case of automatically taking up the cuff, a dry battery is normally used as a power supply for driving the take-up drive in view of portability. The dry battery has a limit in capacity. However, there is a large resistance at the time of taking up and rewinding the cuff. In order to enable the dry battery to be efficiently used, there has been a strong demand to maximally suppress this resistance.
Further, it is difficult to know how much an arm should be inserted when a measurer inserts his arm. If the arm is inserted too deeply or too lightly, there is a problem of being unable to make a precise measurement.